贵州瓮安牛蹄塘组多金属矿层特征及沉积环境

Characteristics of polymetallic seam and depositional environment of Niutitang Formation in Weng'an,Guizhou Province,China

通过对贵州瓮安大信北斗山矿区的多条实测剖面的研究,对寒武系牛蹄塘组开展沉积环境、地层特征、矿物学、岩石学及地球化学研究,探讨瓮安地区寒武系含镍钼钒多金属层的牛蹄塘组的沉积学特征,为寻找该类型矿床提供理论基础。矿层内存在较多脉状、碎屑状黄铁矿和白云岩角砾,指示多金属矿层形成过程中发生过较强烈的构造运动,致使灯影组白云岩冲破上磷矿段至海底,以黄铁矿为主的成矿流体沿裂隙上涌至海底后迅速沉积。岩石组合特征表明,震旦纪末发生了明显海退,沉积环境由局限台地相抬升为陆相;在寒武纪初发生了一次明显海侵,沉积环境变为滨海-陆棚边缘盆地相。

Based on the research of sedimentary environment,stratigraphic characteristics,mineralogy,petrology and geochemistry of Cambrian Niutitang Formation in Beidoushan mining area,Weng'an County of Guizhou Province,the sedimentary characteristics of nickel-molybdenum-vanadium polymetallic layer in Niutitang Formation are discussed in order to provide a theoretical basis for the search for this type of ore deposit.The existence of abundant veins,pyrite fragments and dolomite breccias in the ore layers indicates that strong tectonic movement occurred in the process of ore formation.At the same time,the ore-forming fluid dominated by pyrite migrated upward along the fractures and finally deposited on the seafloor.The characteristics of rock assemblage show that large scale regression occurred in the mining area in the late Sinian Period and resulted in the change of sedimentary environment from limited platform to continental facies,and a large-scale transgression occurred in the early Cambrian,and the sedimentary environment changed again to littoral shelf marginal basin facies.